Field of the Invention
The invention relates to a thermally-polymerizable composition and a combined solution formed thereby, and more particularly, to a solvent-free thermally-polymerizable composition and a combined solution formed by the thermally-polymerizable composition via a solvent-free thermal polymerization reaction.
Description of Related Art
With the rapid development of the information industry, electronic products such as mobile phones, personal digital assistants, and notebook computers have become necessities in everyday life. Among these electronic products, the display is an indispensable human-machine interface. How to provide a lighter and thinner product having better visual effects has always been one of the main objects in the industry. In recent years, the industry further integrated a touch panel and a display panel into a touch display and applied the touch display in various electronic products such that users can directly click the panel to perform various operations, and therefore a more convenient and user-friendly mode of operation is provided.
To make the touch display lighter and thinner and have better visual effect, the industry not only developed various stacking methods, but also strives for breakthroughs in lamination techniques. In the lamination technique aspect, full lamination allows two laminate boards to be completely laminated by an adhesive layer without any gap and air, and therefore the backlight of the display panel can better pass through the stacked layers without a reflection phenomenon caused by different indices of refraction of the transfer media (about 1.52 for the glass protective layer and about 1 for air) and causing reduced brightness of the display screen or glare under strong lighting conditions. Full lamination not only can provide a screen having higher quality, bonding strength and panel impact resistance can also be increased.
FIG. 1 is a schematic of a known touch display adopting a full lamination technique. FIG. 2 is a cross-sectional schematic of a known touch display adopting a full lamination technique. A touch display 1 contains a touch panel 10, an adhesive layer 12, and a display panel 20, wherein the adhesive layer 12 contains a liquid optically clear adhesive (LOCA) 14 and a curable sealant 16.
The LOCA 14 is used to laminate the touch panel 10 to the display panel 20, and the LOCA 14 generally has lower viscosity so as to be uniformly distributed during lamination to achieve better lamination. The LOCA 14 has lower viscosity. The sealant 16 generally has high viscosity, and the main object thereof is to prevent the situation of excess adhesive to the LOCA 14, which is particularly desired for the lamination of large panels. The sealant 16 can further block the LOCA 14 from seeping into a slit 22 between the liquid crystal panel 20 and the frame to prevent contamination to the liquid crystals.
During lamination, the sealant 16 is generally first coated around the edge of the display panel 20 once in a manner of dispensing and curing the sealant 16 at the same time to form a blocking wall having a fixed height. The cured sealant 16 and the display panel 20 form a groove capable of accommodating the LOCA 14. Next, the LOCA 14 is coated in the groove in a Y-shaped or H-shaped dispensing path, and then the upper and lower panels are laminated. During the lamination process, the cured sealant 16 can maintain a fixed gap between the two panels.
Based on the type of the polymer composition, the LOCA 14 currently used by the industry can be divided into rubber optical adhesives and acrylic optical adhesives. The rubber optical adhesive has been in the market longer, and contains, for instance, components of elastic polymer such as polyisoprene, polybutadiene, or polyurethane. Although the rubber optical adhesive has advantages such as good yellowing resistance, flexibility, high adhesion, and high index of refraction, the raw material thereof is more expensive and residual adhesive readily occurs in heavy processing, such that the yield is reduced. As a result, overall production costs are higher.
The acrylic optical adhesive developed later contains, for instance, polyacrylate polymer. Although the acrylic optical adhesive also has the characteristics of high transparency, high adhesion, and good yellowing resistance, the price of the raw material thereof is lower, residual adhesive does not occur and the acrylic optical adhesive can be applied in heavy processing, and overall production costs are lower. Therefore, more and more manufacturers select acrylic optical adhesive as the LOCA 14 for the lamination of the touch panel 10 and the display panel 20.
Currently, different LOCAs 14 are developed by the industry for the demands of different products and different lamination machines, such as a LOCA 14 having a specific dielectric constant or viscosity range, and a sealant 16 matching the specific LOCA 14 is manufactured in addition.
In general, as described above, the lamination state between the touch panel and the display panel can be done via a sealant and a LOCA having optical transparency. However, since the viscosities of the sealant and the LOCA are different, the indices of refraction and optical properties of the sealant and the LOCA often do not match. As a result, a clearly-distinguishable interface is produced at the junction of the sealant and the LOCA, and visual effects are affected.